Re: concept of a permissive domain

[Joshua Brindle <method@manicmethod.com>]

Eric Paris wrote:
> So there was a brief conversation between dan, karl, and myself today
> about implementing a permissive subject domain.  Basically there would
> be some new language construct possibly "permissive httpd_t true;" which
> would then set a flag.  If this flag was set, all denials would be
> logged but the operation would be permitted.  This would make it
> possible to create a type_exec_t and type_t for your new domain, mark it
> as permissive/unconfined and run it as long as you like.  Once you get
> all your new allow rules you just remove the permissive bit.  You didn't
> have to setenforce the whole system.
>
> First thought from Karl was to use the 'char primary' field of the
> struct type_datum.  Seems reasonable enough, after we have that
> information in kernel it shouldn't take me too much playing around in
> avc_has_perm_noaudit to check if this flag is set on a denial.  I don't
> think slowing down the denial path a little by having to call back in to
> see if this flag was set for a given source sid is that big of deal.
> Maybe I could keep it just about as fast by adding more flags
> audit_allow_once (can't really reuse audit_allow) to the avd or
> something like that, but it seems like a large waste of space to carry
> another set of audit flags that won't be used much.
>
> Thoughts?  Other ways to implement this?  Problems with the basic premis
> of an unconfined domain?
>   

This is asking for all kinds of problems. Writes to directories without 
type transitions means after a policy is written, if the correct 
refpolicy interface is used that defines a transition, then any files 
written during 'permissive mode' won't be accessible. Domain transitions 
are in the same boat, imagine what domains processes could end up 
running in during this. We need to tread very carefully here, and there 
are interesting ramifications to transitioning to and from the 
permissive domains during runtime. If an application has a transition to 
the permissive domain a new attack vector was just introduced. I know 
this can be helpful and its better than running the entire system in 
permissive but it can also be dangerous.


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